This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Chemically selective ultramicroelectrodes form the backbone of the resource technology and the support of our user group. Broadly these electrodes can be divided into potentiometric, based on ion selective liquid membranes, and amperometric, based on redox chemistry at a metal or carbon interface. Enzyme assisted electrodes are dealt with in a separate project. Whereas the development of the potentiometric sensor has made significant progress towards a simple disposable ion selective microelectrode, the same cannot be said of the amperometric variety. This is a solid-state sensor design based on a metal (gold, platinum) or carbon core. The final tip diameters are approximately 4 microns. Construction has been tedious, time consuming, with a variable final product. There are no commercial sources for these sensors. To date the BRC has developed, to application, basic amperometric sensors for oxygen, nitric oxide, ascorbate and hydrogen peroxide. The same bodies are used for enzyme assisted, which cover glucose, glutamate and lactate. Improving the efficiency and fabrication of chemically selective microelectrodes is an ongoing project.